A vision system, as used herein, is any arrangement of optical elements supported on a suitable structural framework for purposes of viewing by a human individual. For binocular vision systems, a structural framework supports optics for each eye, referred to herein as monocular optics and it is the structural framework that establishes the separation of the monocular optics, so as to correspond with the interpupillary distance (IPD) of a particular human individual.
In the case of hands-free vision systems, i.e., those supported against gravity by engagement with the human body, the structural framework additionally establishes the relative positioning between the optics and the eyes of a particular individual. For hands-free vision systems configured for low magnification/wide viewing angle use, anthropometric differences between individual users can be met by a single structural framework design fabricated in a small number of standardized sizes. Eyeglasses are an example of such a system. However, at higher magnification, light emerges from the monocular optics through respective exit pupils, the diameter of which is established by the configuration of optics and by the mechanical components that maintain that configuration (the exit pupil can be understood as the image of the aperture stop formed at the output of the optical system by the interposing optics). When the exit pupil is not properly aligned with the ocular pupil, the resulting image appears as if cutoff by a phenomenon referred to as “vignetting.” Similar issues arise in optical devices having constrained fields-of-view for reasons other than magnification. For example, in optical devices having active components in the optical path, such as in night vision goggles, the fields-of-view may be constrained by not only refractive optical elements, but light amplification or intensification mechanisms as well (e.g., photocathodes, micro-channel plates, cascaded image intensifier tubes, etc.).
A set of binoculars, or simply “binoculars” as the term is commonly used, is such a binocular vision system; it combines two monocular telescopes, for viewing distant objects with both eyes of a viewer. To align each monocular telescope to a corresponding eye of a particular individual, conventional binoculars provide a mechanism by which the distance between the optical axes of the eyepiece optics can be adjusted to the IPD. Such adjustment mechanisms include single hinge joint implementations, such as that illustrated in FIG. 1A, in which both monoculars pivot about the same axis of rotation defined through hinge joint 110. Another conventional binocular adjustment mechanism is the lateral bridge, such as that illustrated in FIG. 1B, in which each monocular is coupled to a central bridge 115 through a separate hinge joint 120a-120b, and each monocular pivots about separated axes of rotation. In each of these implementations, the IPD setting, i.e., the state in which the distance between the optical axes of the binocular eyepieces matches the IPD for a particular viewer, is achieved by rotation of the monoculars about the one or more hinge joint axes.
It is considered beneficial that many conventional binocular designs can be folded at the hinge joints into a compact configuration for purposes of storage. However, such folding relocates the optical axes and, consequently, it is necessary to reestablish the IPD setting at the time the binoculars are next used. Additionally, since the rotational axis through the hinge is constrained to parallelism with the optical axes of the monoculars (otherwise rotation about the hinge joint would skew the optical axes away from the sighting direction), the axes about which the folding is realized is likewise constrained. In hands-free implementations that allow relocation of one or more monoculars away from the visual path by articulation at the hinge joint, the parallelism constraint on the folding axes limits the storage compactness, i.e., the degree to which a monocular extends from the human body during rotation thereof about the corresponding hinge joint. In certain conventional designs, the monoculars can be sufficiently removed from the eyes and face only through a long swing radius that may be prohibitive for certain deployment scenarios.